[PATCH 2/2] drm/edid: Have cea_db_offsets() zero start/end when the data block collection isn't found

[Jean Delvare]

Hi Ville,

On Mon,  2 Sep 2019 16:15:46 +0300, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> Let's make cea_db_offsets() a bit more convenient to use by
> setting the start/end offsets to zero whenever the data block
> collection isn't present. This makes it safe for the caller
> to blindly iterate the data blocks even if there are none.
> 
> Cc: Jean Delvare <jdelvare at suse.de>
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/drm_edid.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 7b3072fc550b..e5905dc764c1 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -3690,6 +3690,9 @@ cea_revision(const u8 *cea)
>  static int
>  cea_db_offsets(const u8 *cea, int *start, int *end)
>  {
> +	*start = 0;
> +	*end = 0;
> +
>  	if (cea_revision(cea) < 3)
>  		return -ENOTSUPP;
>  
> @@ -4116,10 +4119,7 @@ static void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid)
>  	if (cea_revision(cea) >= 3) {
>  		int i, start, end;
>  
> -		if (cea_db_offsets(cea, &start, &end)) {
> -			start = 0;
> -			end = 0;
> -		}
> +		cea_db_offsets(cea, &start, &end);
>  
>  		for_each_cea_db(cea, i, start, end) {
>  			db = &cea[i];

Not sure if that's really needed. As it stands there's only one
function which wants to continue after cea_db_offsets() fails, all
others just bail out at that point. Now that cea_db_offsets() checks
for revision >= 3, the construct above could simply become:

	int i, start, end;

	if (cea_db_offsets(cea, &start, &end) == 0) {
		for_each_cea_db(cea, i, start, end) {
			db = &cea[i];

which is IMHO more elegant and does not require zeroing start and end
in cea_db_offsets().

-- 
Jean Delvare
SUSE L3 Support